Derrick



July 23, 1935. J. DE vou 2,008,785

' DERRICK Filed March 19, 1952 mew/Z 07:

J4ME6 4.. a? V00,

and lifting through a boom 3.

Patented July 23, 1935 UNITED STATES PATENT OFFICE 2 Claims.

Thisinvention relates to derricks used in the construction of bridges.These derricks generally mustbe moved along the bridge during itsconstruction, one of the objects of the present invention being toproperly guy them in position while they are being moved. Other objectswill.

be understood from the following.

Having reference to the accompanying drawing which illustrates aspecific example of the invention:

Figure 1 is a cross-sectional side elevation.

Figure 2 is a cross-section from the line II--II in Figure 1.

This drawing shows a hollow fabricated steel mast I rotatably carried ona movable support 2 This is like all bridge derricks excepting that thefoot-block 4 is constructed larger thanis ordinarily the case. The topof this mast is positioned by guys which extend from it to supportingpoints which may be on either the bridge or river shore. In thisinstance the mast is guyed by cables 6 and l which are fixed to oppositesides of the masts spider and extend to supporting points 8 and back tothe top of the mast where they pass over sheaves 9 and downwardlythrough the inside of the mast l The portions of the cables between themasts spider and the supporting points 8 are-practically horizontal andat right angles to the mast i. This results from the points 8 beingarranged about at the level of the top of the mast l, as is shown byFigure 1. Two more sheaves I are fixed to the mast adjacent its bottom,the cables 6 and l passing around them and extending to drums l I and 12which are'mounted on the support 2. v

When it is necessary to move the mast along the bridge one of the drumsis simply let out and the other one taken invso that properlyproportioned opposing forces may always be maintained at the top of themast, this being possible because the cables extend horizontally fromthe mast. These forces maybe properly applied to guy the mast intoposition both during movement of the lifting rig and While it is inposition. Preferably the drums are separated as illustrated because thepull on the mast top can then be proportioned to meet varying loadconditions on the boom 3. If desired, however, the ends of thecables 6and. Iv may be joined and these cables given a few wraps around a singledrum. Then when this drum is rotated one cable will be let out the sameamount the other cable'is taken in.

It should be understood that the support 2 is moved by a separate forceand that the drums l l and.v 12 are used to carry the excess of the.cables 0 and "l over'what is actually being used for guying purposes,and to maintain tension on these cables during movement of the liftingrig.

Although a specific form of this apparatus has been shown and describedin accordance with the patent statutes, it is not intended to limit thescope of the invention exactly thereto, except as defined by thefollowing claims.

I claim:

1. A bridge derrick including a support constructed for movement along abridge, a mast carried by said support, guys arranged toextendpractically horizontally from said mast to suitable supporting pointsand means for varying the relative lengths of said guys during movementof said support. 1

2. A bridge derrick including a support co structed for movement along abridge, a mast carried by'said support, sheaves fixed to the top of saidmast, guys extending practically horizontally from suitable supportingpoints towards said support by way of said sheaves and means carried bysaid support for varying the relative lengths of said guys duringmovement of the former.

JAMES L. DE VOU.

